Laser Scanner Coordinate Correction for fθ Lens Distortion
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Solution Overview
Problem
The fθ lens in laser processing apparatuses causes progressive distortion of the laser beam, leading to inaccuracies in forming through holes at the outer circumference of wafers, even with precise control of the X-axis and Y-axis galvanometer scanners.
Innovation Solution
A method that includes recording and correcting the coordinates of the pulsed laser beam application positions using a coordinate recording section and a corrective value recording section, with the image capturing unit positioning and capturing processed marks to detect shifts and calculate corrective values for accurate processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the X-axis and Y-axis galvanometer scanners are controlled highly accurately, then the laser beam positioning should be precise, but the fθ lens distortion still causes through holes to shift from the electrodes at outer circumferential regions
Solution Approach 1:
The patent introduces an intermediary correction mechanism between the galvanometer scanner control and the actual laser beam positioning. The control unit calculates corrected scanner drive values by applying distortion correction values to the original scanner commands, creating an intermediate correction layer that compensates for fθ lens distortion without requiring changes to the scanner hardware or control precision
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise application of the pulsed laser beam to electrodes on wafers, ensuring accurate formation of through holes by correcting for distortions caused by the fθ lens, thereby improving processing accuracy.
Implementation Method 1
an fθ lens for converging the pulsed laser beam that has been swung in the X-axis direction and the Y-axis direction onto the workpiece held on the chuck table
Implementation Method 2
an X-axis galvanometer scanner for swinging a pulsed laser beam emitted from the laser oscillator in the X-axis direction, a Y-axis galvanometer scanner for swinging the pulsed laser beam emitted from the laser oscillator in the Y-axis direction
Data Source
AI summary
A method of adjusting a laser processing apparatus includes controlling an X-axis galvanometer scanner and a Y-axis galvanometer scanner on the basis of X coordinates and Y coordinates recorded in a coordinate recording section to apply a pulsed laser beam to a workpiece, thereby processing the workpiece, actuating an X-axis moving mechanism and a Y-axis moving mechanism on the basis of the X coordinates and the Y coordinates recorded in the coordinate recording section and causing an image capturing unit to capture an image of processed marks on the workpiece, and detecting shifts between X coordinates and Y coordinates of the processed marks whose image has been captured in the processed mark image capturing step and the X coordinates and the Y coordinates recorded in the coordinate recording section, and recording corrective values in a corrective value recording section.